1. Technical Field
The present invention relates to a post-processing apparatus for performing post-processing such as binding processing and folding processing on sheets that are carried out of an image formation apparatus such as a copier and printer, and more particularly, to improvements in the folding mechanism for folding a sheet fed from the image formation apparatus.
2. Description of the Related Art
Generally, post-processing apparatuses are widely known which perform post-processing on image-formed sheets corresponding to their use. As an aspect of the post-processing, used frequently is the processing for collating and collecting sheets and binding the sheets using a stapler. In this case, it is necessary to perform folding processing on sheets to bind.
For example, Patent Document 1 proposes a post-processing apparatus provided with a processing mechanism for guiding image-formed sheets to a processing tray to bind without performing folding processing on the sheets, and a magazine binding processing mechanism for guiding sheets to a collection section different from the processing tray, binding the center of the sheets, and then folding the sheets.
The apparatus in the Document is not provided with a mechanism for folding image-formed sheets on a sheet-by-sheet basis and performing binding processing on the sheets on the processing tray. Therefore, the Document does not propose a post-processing finish for mixing sheets which are fed to the tray without undergoing the folding processing and sheets which are fed to the tray after undergoing the folding processing and binding the sheets.
Similarly, Patent Document 2 discloses a post-processing apparatus provided with the magazine binding processing mechanism, and in the apparatus, a folding mechanism is proposed in which a mechanism for folding a bunch of collated and collected sheets in the center folds sheets on a sheet-by-sheet basis. In the Document, the mechanism is disclosed as a mechanism for storing the sheets folded on a sheet-by-sheet basis in a storage stocker in this state.    [Patent Document 1] Japanese Patent Application Publication No. 2008-184324 (FIG. 1)    [Patent Document 2] Japanese Patent Application Publication No. 2002-308521 (FIG. 2)
As described above, as the post-processing apparatus for performing binding processing on image-formed sheets, adopted conventionally is the processing method for collating and collecting the sheets to perform the binding processing without performing the folding processing, binding a bunch of collated and collected sheets and then performing the folding processing on the sheets, or performing the folding processing on the sheets on a sheet-by-sheet basis.
In addition, as a finish form, there is a case of mixing sheets without undergoing the folding processing and folding-processed sheets (for example, Z-folded sheets) in collating and collecting sheets. For example, such a form is known as a finish method for mixing a Z-folded A3-size sheet with A4-size sheets and binding the entire sheets in book form.
Then, in the conventional post-processing apparatus provided with the magazine binding mechanism for performing saddle stitching on a bunch of sheets and folding the sheets, and the end stitching mechanism for binding a bunch of sheets without performing the folding processing, to perform the above-mentioned mixing binding processing, it is necessary to provide a sheet folding unit on the upstream side of the post-processing apparatus.
Therefore, the inventor of the invention arrived at the idea of folding sheets on a sheet-by-sheet basis in the folding mechanism for folding a bunch of sheets, feeding the sheet to the processing tray, and mixing the sheet with sheets without the folding processing.
In this case, the above-mentioned Patent Document 2 discloses that a folding processing section is provided with folding rollers to perform two-folding, and folding rollers to perform three-folding, the folding processing is performed using the two-folding rollers in magazine binding, and that a single sheet is subjected to the folding processing by the two-folding rollers, and then the folding processing by the three-folding rollers. However, to prepare the rollers for two-folding and three-folding in the folding processing section, it is necessary to provide folding rolls and folding plates (folding blades) individually and include driving mechanisms therefor, and there is the problem that the apparatus becomes complicated and large.
It is an object of the invention to provide a post-processing apparatus for enabling a bunch of sheets and a single sheet to be folded in simplified structure, and further enabling the folded sheet and sheets that are not folded to be mixed and bound.